kink

A kink is a bend or a twist in an otherwise straight line, like a kink in a garden hose that blocks water from flowing freely.

When something kinks, it bends to form a kink or curl — if your hair kinks in the rain, it gets tightly curly. You can also have a kink in your neck, a tight muscle that cramps painfully. Yet another kind of kink is a problem, complication, or weakness in a plan: "The major kink in her plan turned out to be that no one was interested in buying hand-knitted cat sweaters."